Porous polymers have been found useful in many applications. Among various polymers, epoxy can be used in a wide range of applications such as coatings, adhesives and composite materials due to its great versatility, low shrinkage, good chemical resistance, low dielectric constant and outstanding adhesion.
Different methods have been developed to produce porous polymers of different morphology. One of the methods commonly used is chemical induced phase separation (CIPS). In CIPS, a homogeneous solution of monomers or prepolymers and a solvent becomes phase separated during polymerization, and a porous polymer might be obtained by heating the solution to a temperature higher than the glass transition temperature (Tg) of the polymer to remove the solvent. To obtain a porous polymer of good quality, the heating is normally done by a stepwise manner, that is, to heat the solution of monomers or prepolymers and a solvent to a temperature sufficient to form a polymeric gel first, and then heat the polymeric gel to a temperature above the Tg of the polymer for a certain period to obtain a stable polymer. For a thermosetting polymer (e.g., epoxy), the term “gel” refers to a state where the polymer is partially cross-linked and can no longer be dissolved by a solvent while at least part of the original solvent remains therein.
Porous epoxy can be made by CIPS, too. By heating up the solution of diglycidylether bisphenol-A epoxy (DGEBA) and 2,2′-bis(4-amino-cyclohexyl)propane (as a curing agent) in the presence of hexane and/or cyclohexane (as a solvent), a porous epoxy network can be prepared. By adjusting reaction conditions, the morphology of the porous epoxy can be varied (see, J Kiefer, Polymer, 37(25), 1996, pp. 5715-5725). However, the epoxy network obtained by the above method is with pores of closed cells.
By incorporating poly(vinylmethyl)ether into epoxy resin, one may obtain epoxy networks with open pores. However, poly(vinylmethyl)ether is difficult to be removed, which may affect the stability of the network and cause problems.
Therefore, there is still a need for providing a new process for manufacturing a porous epoxy with open pores.